Enhancing Metallocene Catalyst Activity: Utilizing Layered Double Hydroxide for Ethylene-Propylene Copolymerization

This study reports the heterogenization of metallocene catalysts on sodium dodecyl sulfate (DDS)-modified layered double hydroxides (LDHs) for efficient ethylene-propylene (EP) slurry-phase copolymerization. The LDH support offers considerable compositional tunability. NiFe LDHs with different anions (CO32-,NO3-,and DDS-) and metallic compositions are applied as support for the metallocene catalysts; these significantly influence the catalytic properties of the heterogenized catalyst system. The supported-catalyst intercalating DDS- anion in the galleries of NiFe and ZnAl LDHs demonstrates a high catalytic activity. They produce EP copolymers with high molecular weights (Mw) and wide polydispersity, compared with the homogeneous Zr catalyst. Further, the supported catalyst complex containing CO32- anion produces EP with a tenfold high Mw and demonstrate subdued catalytic activity. The higher basicity of the support is associated with the enhanced activity and the wider polydispersity of the EP pertaining to the different interactions of the catalyst molecule with the support. Overall, Ni-containing LDH favors a higher activity, whereas Fe-containing LDH favors a higher Mw. Therefore, NiFe-based LDH results in both higher activity and molecular weight. 13C and 27Al magnetic angle spinning solid-state nuclear magnetic resonance confirm the formation of the supported catalyst complex.